#include <iostream>
using std::cout;
using std::endl;

void func(const int & x,int & y){
    //x = 100;//error 常引用
    y = 200;
}

void test0(){
    int a = 1, b = 2;
    func(a,b);
}

int main(void){
    test0();
    return 0;
}
